Corrosion inhibition



CORROSION INHIBITION John F. Eberhard, Tulsa, Okla., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Apr. 18, 1958, Ser. No. 729,242

3 Claims. (Cl. 252-151) The present invention relates to the inhibition of metal corrosion and more particularly relates to a new and useful composition which prevents the corrosion of metals when they are in contact with acids.

Most known corrosion inhibitors decompose in the presence of oxidizing acids, such as dilute nitric acid and the like. Further, many of the useful inhibitors have very narrow limits of operation necessitating the use of customer-tailored acid compositions.

It is therefore an object of the present invention to provide an acid-system metal corrosion inhibitor composition which is operative over a wide range of concentrations of both oxidizing acids and non-oxidizing acids. Another object of the present invention is to provide a corrosion inhibitor composition which will not decompose under oxidizing conditions. These and other objects will become apparent to those skilled in the art from the following specification and claims.

It has now been found that acid corrosion of metals, particularly that caused by the oxidizing acids, can be inhibited by mixing with the acid system a composition containing propargyl sulfide and one orv more of the thio compounds of the class alkanedithiols, mercaptoalkanols', mercaptoalkanoic acids, thiolalkanoic acids, alkyl sulfides, or inorganic sulfides. Good results are obtained when the inhibitor composition is employed in an amount of from 0.0625 to 1.00 percent by volume of ultimate composition.

In accordance with the present invention, when the composition of the present invention is mixed with an acid, i.e., a mineral acid such as nitric, hydrochloric, sulfuric, phosphoric or perchloric acid or the lower organic acids such as acetic and the like in an amount of from 0.0625 percent to 1.0 percent and preferably from 0.125 percent to about 0.5 percent by volume of the ultimate composition, the corrosion of metal surfaces in contact therewith is substantially inhibited.

Various combinations of sulfur-containing compounds may be employed to prepare the inhibitor compositions of the present invention. Thus, propargyl sulfide can be admixed with one or more of the following sulfur-containing compounds, i.e., ethanedithiol, thiolacetic acid, mercaptoacetic acid, ethyl sulfide, hydrogen sulfide, ferrous sulfide, and the like. The ratios of sulfur-containing compound to propargyl sulfide which are Within the scope of the present invention are from 0.25 to 1.0 part by volume of sulfur compound per volume of propargyl sulfide.

The following examples are illustrative of the present invention but are not to be construed as limiting.

Examples 1-20 Corrosion rate data on various mixtures of propargyl 2,963,439 Patented Dec. 6, 1960 sulfide and sulfur compound as the active inhibitor in 10 percent nitric acid.

Volume acid150 ml. (10 percent nitric acid). Metal-AISI 1010 mild steel coupon (2.75 x 1.0" x 0.12) duration of test 6 hours.

Example Inhibitor Concentration 'Iempera- Corrosion No. in percent by volume ture F.) Rate (lbs/ ftF/d'a'y) .4 percent propargyl sulfide 0.172 .5 percent ethanedithioL.-- 80 0. 001 .25 percent propargyl sulfi 80 0. 0001 0.25 percent ethanedlthiol. do 150 0.0023 0.5 percent mereaptoethanol 80 0. 006 0.25 percent propargyl sulfide 80 0. 0008 0.25 percent mercaptoethanol. d0 150 0.005 0.5 percent thiolacetic acid 80 0. 097 0.25 percent propargyl sulfide 80 0. 0007 0.25 percent thiolacetic acid. d0 150 0.0025 0.5 percent mercaptoacetic acid 80 0.122 0.25 percent propargyl sulfide 80 0. 0001 0.25 percent mercaptoacetic acid. -do 150 0.0031 0.5 percent ethyl sulfide 80 1. 0 0.25 percent propargyl sulfide 80 0. 004

0.25 percent ethyl sulfide. do 150 0.007 0.5 percent hydrogen sulfide 80 1. 0 0.25 percent propargyl sulfide sat- 80 0. 0003 urated with hydrogen sulfide. 0.5 percent ferrous sulfide 80 0. 205 0.4 percent propargyl sulfide 0.5 80 0. 0004 percent ferrous sulfide.

Examples 21-26 Volume acid-A50 ml. 10 percent nitric acid.

Metal-AISI 1010 mild steel coupons (2.75 x 1.0" x 0.12"). Length of test-6 hours.

Temperature-80 F.

Concentration Example N0. Inhibitor Corrosion Rate (percent by (lbsJftE/day) volume) None too high to measure.

Examples 27-37 Length of tests-6 hours. Temperature-80 F.

Cone. Propargyl Cone. other Sulfur Corrosion Test No. Sulfide Containing Compound Rate (1bs.l

(percent (percent by vol.) ftJ/day) by vol.)

0. 5 None 0.172. 0. 4 0.10 ethanedithiol 0.028. 0.30 0.20 ethanedithioL. 0.0032. 0. 25 0.25 ethanedithioL- 0.0001. 0. 125 0.375 ethanedithiol- 0.0007. None 0.5 ethanedithiol 0.001. 0. 4 0.1 mercaptoacetic acid 0.068. 0.3 0.2 mercaptoacetic acid 0.0009 0. 25 0.25 mercaptoacetic acid---" 0.0001 0. 125 0.375 mercaptoacetic acld. 0.014. None 0.5 mercaptoacetic acid 0.122.

3 Examples 38-48 Additional tests were run, varying the acid concentratron and temperature to show the effectiveness of the inhibitor.

Volume aicd150 ml., nitric acid. Inhibitor-0.5 percent (by volume) of a mixture of 1 part by volume propargyl sulfide plus 1 part 1,2-ethanedithiol.

Metal-AISI 1010 mild steel coupons (2.75 x 1.0 x 0.125"). Length of test-6 hours.

Cone, Test No. Nitric Tempera- Corrosion Rate Acid, ture F.) (lbs/ftfl/day) percent 10 80 0.0001. 10 150 0.0023 15 80 0.0006 15 150 0.0081 20 80 0.0084 20 150 0.014. 25 80 0.0091. 25 150 too high to meas. 30 80 0.023. 30 150 too high to meas. 50 80 Do.

Examples 49-58 Various metals were exposed to other acids of industrial importance using an inhibitor composition of the instant invention. The results indicated below show the inhibitor is effective in these other acids.

Inthgbiltor: one part by volume propargyl sulfide to 1 part 1,2 ethancdi- Volume acid-150 ml. Metal-A181 1020 mild steel coupons (2.75+1.0 x 0.125). Conditions of test-16 hours exposure at 150 F.

Concentration Corrosion Test No. Acid Medium Inhibitor Rate (lbs./

(Percent ftfl/day) by volume) 10 percent Hydrochloric"--- Non 1. o 0. 0.0010 percent Acetic None 0. 140 d0 0. 0. 0002 5 percent Sulfuric- None 0. 185 (10 0. 0.0087 5 percent Phosph None .0. 086 do 0. 5 0. 00091 10 percent None 0. do-- 0. 0. 0003 4 Examples 59-68 A series of metals was exposed to dilute nitric acid inhibited with one of the inhibitor compositions of this invention. The inhibitor was a -50 mixture of propargyl sulfide and 1,2-ethanedthiol.

Volume Acid-150 ml.

Length of Test-6 hours. Temperature F.

Cone. Inhibitor, (percent by volume) Corrosion Rate Metal Coupon (lbs/ttJ/day) Test No.

too high to Ineas. 0. 2.

References Citedin the file of this patent UNITED STATES PATENTS 1,911,446 Grebe et a1. May 30, 1933 2,215,092 Beekhuis et a1 Sept. 17, 1940 2,411,791 Hunt et a1. Nov. 26, 1946 2,461,359 Viles et a1. Feb. 8, 1949 2,474,603 Viles et a1 June 28, 1949 2,613,131 Barnes et a1. Oct. 7, 1952v 2,814,593 Beiswanger et al. Nov. 26, 1957 

1. A METAL CORROSION INHIBITING COMPOSITION COMPRISING ONE PART BY VOLUME OF PROPARGYL SULFIDE AND FROM 0.25 TO 1.0 PART BY VOLUME OF A SULFUR-CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF ETHANEDITHIOL, THIOLACETIC ACID, MERCAPTOACETIC ACID, ETHYL SULFIDE, HYDROGEN SULFIDE, AND FERROUS SULFIDE. 